Semi-related but very valuable advice, if well-known - when I was off sick the council brought a complaint against me. They actually lied and implied criminal behaviour (fraud) on my part (also not turning over all the evidence to the tribunal that followed). So here's the important bit:

DO IT IN WRITING AND KEEP COPIES OF EVERYTHING, EVERYTHING YOU WRITE, EVERYTHING THEY SEND YOU. INSIST ON IT BEING ON PAPER (NOT TELEPHONE), AND PRINT EMAILS OUT.

I could rebut almost everything bad they said about me. The tribunal threw out their case before I even turned up.

(I know this is obvious and everyone says get it in writing, but things would be smoother if people actually did).